/Engine/Source/Runtime/GeometryCore/Public/Spatial/SparseDynamicOctree3.h
Warning: result here appears to be unstable (due to optimization?) if any of the position values are on the border of a cell (in testing, pragma-optimization-disabled code produced off-by-one result from calling this function)
[FVector3i](API\Runtime\GeometryCore\FVector3i) PointToIndex ( uint32 Level, const FVector3d & Position ) const